To prevent vegetation from obstructing roads, utility lines and the like, various devices have been proposed. For example, U.S. Pat. No. 3,343,575 to Trout and U.S. Pat. No. 4,813,142 to Manno each describes a tree-trimming rotary saw attachment mounted to the end of a dipperstick of a conventional backhoe assembly. The attachments are designed to engage vegetation at ground level but can also engage elevated vegetation that falls within the limited reach of the assembly. These attachments however are ineffective for clearing obstructions caused by tall trees and the like.
Another example, U.S. Pat. No. 4,411,070 to Boyum et al., describes a tree-trimming apparatus that is capable of reaching beyond the limited reach of attachments like those described by Trout and Manno. The reach of the apparatus is extended by combining a telescoping boom having a rotary saw attached to the end thereof, a modified flat bed truck having a rotatable turntable mounted thereto and a pedestal pivotally mounted to the turntable. The telescoping boom is pivotally mounted on the pedestal and controlled from an operator's station mounted on one side of the pedestal. The apparatus is powered by a hydraulic system partially supported by the turntable. One shortcoming of the Boynum et al. apparatus is its complexity. For example, the apparatus relies on the rotatable turntable for imparting lateral movement to the telescoping boom. In practice, this arrangement often leads to breakdowns of the apparatus because of the unreliability of the complicated assembly in the turntable used to operatively connect those portions of the hydraulic system that rotate with the telescoping boom to those that do not.